Sound reproducer



Aug. 17 1926.

F. J. KAEHNI ET AL SOUND REPRODUCER Filed May 16, 1922 2 Sheets-SheetLl Aug. 17 1926. 1,596,045

F. .1. KAEHNI ET AL SOUND REPRODUCER Filed May 16 1922 2 Sheets-Sheet 2 6- mmnlmnnm 7 34 Zia -5 5&5

ljvldzjevz qzaj arm (4L96 Patented Aug, 17,

UNITED STATES ATENT FFICE,

FRANK T. KAEHINI AND WILLIAM L. KAEHNI, OF CLEVELAND, OHIO, ASSIGNORS TO THE CLEVELAND TRUST COMPANY, TRUSTEE, OF CLEVELAND, OHIU, A. 00330- TION' OF OHIO.

SOUND REYRODUGER.

Application filed May 16, 1922. Serial No. 561,415.

This invention relates to a device for reproducing sound transmitted electro-magnetically. The device is especially useful in connection with radio telephony and may be advantageously employed to amplify as well as reproduce the sound transmitted. The general object of the invention is to provide simple and efiective mechanism operable by electromagnetic impulses to reproduce sound without distortion irrespective of the amplification of the current va-' riations transmitted.

The prior devices for reproducing sound now in use in radio telephony are of three general types, each of which has disadvantages which it is the object of our invention to overcome.

The first type comprises a simple telephone receiver wherein there is an iron diaphragm acting as an armature for a permanent magnet which is strengthened and weakened by the electric current. Such devices result in distortion of the sound whenever the power is great enough to operate with a horn, for the reason that the diaphragm must have such amplitude that at different times it is at materially varying distances from the pole pieces, so that a given magnetic strength has varying action upon it, the result of which is that a constant power input causes a variable sound output, depending on the distances between the poles and the diaphragm.

A second type of reproducer in use employs an intermcdiately pivoted armature operating between two pairs of poles, the poles of like sign being onthe same side of the armature but being spaced to stand on opposite sides of the pivot, and there being a winding, the current through which strengthens one of the north poles and the diagonally opposite south pole, and at the same time weakens the other north pole and the diagonally opposite south pole. The armature being linked to a suitable diaphragm reproduces the sound, but here again distortion occurs if there is a wide range of power input, for instead of continuing to act in the same manner, the impressed field in such circumstances becomes greater than the permanent field and acts in the opposite direction so that a north pole for in stance, instead of becoming simply a weaker north pole becomes a south pole. This causes poor reproduction of sound when increased volume is attempted.

The third type of amplifying reproducer now in use, employs an electro-magnetic field which is supplied from outside source of electrical power and within this field is located a moving coil which connects with the diaphragm. A disadvantage of this type of construction resides in the necessity for making electric connection with the coil, which must be free to vibrate according to the telephone currents.

Our reproduceris designed to eliminate the most of the disadvantages of the foregoing types of reproducers and at the same time maintain a high efficiency. In accomplishing this we have provided a device which avoids the employment of permanent magnets and avoids any electric connection with the movable element. Broadly, the devicecomprises the employment with a diaphragm of a coil, an energized circuit therefor, and an electronic valve for controlling the flow of current in the winding. Ve prefer to employ for this purpose two iron-clad solenoids suitably spaced and mounted end to end in a rigid holder, and we utilize the movement of an armature lever either by direct connection with a phonograph diaphragm. or by a multiplying connection therewith, as desired.

- We may provide simply a holder carrying a large diaphragm and a link from the armature lever directly to the center of the diaphragm, or we may use a small diaphragm and multiplying leverage between it and the armature lever. ferred method and one productive of highly desirable results with great simplicity and convenience may be readily effected by using an ordinary phonograph reproducer, the needle of which rests on the armature lever. In such case it is entirely feasible to simply stand our solenoid unit within the ordinary phonograph cabinet at the side of the rotary table, with the armature projecting upwardly and with its movementin a path approximately radial of the rotary table, the reproducing needle being rested on the top of the armature lever. The armature lever thus gives to the phonograph needle the lateral movements corresponding to those'ordinarily given by the groove in the disk record, and the sound is emittedthrough the The second prephonograph horn. Our invention includes broadly this method of utilizing armature vibrations however produced, as well as the means we have invented for producing such vibrations.

Our invention is illustrated in the drawings hereof and is hereinafter fully described and the essential features are summarized in the claims.

In the drawings, Fig. 1 is a front elevation of our reproducing and amplifying device or loud speaker of a form employing the large diaphragm in direct connection with the armature; Fig. 2 is a vertical section through such device; Fig. 3 is a vertical section on a larger scale through the solenoid mechanism along the axis thereof, being in a plane parallel with Fig. 2; Fig. 4 is an end view of the solenoid mechanism; Fig. 5 is a detail illustrating means which may be employed for clamping the diaphragm to the holder body; Fig. 6 is an elevation of the combination of our solenoid mechanism with the phonograph reproducer and sound arm, the solenoid mechanism being shown in end view with its casing sectioned; 7 is an enlarged view of the solenoid mechanism arranged for this adaptation in side elevation; Fig. 8 is a diagram of the circuits, tubes, batteries, etc., employed in energizing the solenoids.

As shown in Fig. 3, 10, 10 indicate two solenoid windings, each suitably ironclad, as for instance between iron cups 11 and the iron disk 12 screwed therein to entirely house the coil. Each disk 12 carries an adjustable plug 13 mounted in the disk and projecting into the solenoid opening. This plug is formed so that it may be conveniently adjusted as by being threaded in the disk 12 and having a screw driver slot 14 in its end and carrying a jam nut 15 engaging the face of the disk 12.

The two ironclad solenoids are rigidly carried opposite each other as shown in Fig. 3. To effect this we have shown each iron cup 11 as threaded at its inner end and as screwing into a non-magnetic ring 20. Suitably carried by the non-magnetic ring in a position equi-distant between the solenoids is the armature lever which is shown as carried by a leaf spring 31 mounted in the screw 32 adjustably clamped by nuts 33 and '34 to the ring 20. This armature lever 30 carries magnetic cores 35 extending in opposite directions therefrom and entering the solenoid openings respectively through sufficiently large openings in the ironclad cups so that the cores will be out of contact therewith.

It Will be seen that with such a construe tion as described, if the current through one solenoid is strengthened, another through the other solenoid weakened, by the action of suitable electric valves, an incoming alternating current may thus cause a vibration of the armature lever 30 corresponding to the frequency and wave form of the incoming current. The armature lever 30 is connected in a suitable manner with a suitable diaphragm to give a corresponding sound reproduction.

As illustrated in Figs. 1, 2 and 5, 4O indicates a suitable holder for a comparatively large diaphragm 41 which is connected by a link 42 with the armature lever 30. The holder is shown as a dish shaped metal member provided with suitable supporting legs 45, though other form of holder may be employed as desired. As shown the dish shaped member has an outstanding peripheral flange 46 to which is fastened an inwardly flanged ring 50. This ring is l.- shaped in cross section and bears at its outer portion against the edge of the flange 46 while its inner portion overhangs the diaphragm '41. Suitable screws 52 passing through the ring and into the flange 46 serve to cause the ring to clamp the diaphragm to the flange. A pair of gaskets 53 and 54 lie on opposite sides of the diaphragm and thus enable its edge to be effectively clamped in place in a sufficiently yielding manner to allow proper vibration thereof, as will be readily understood.

In the loud speaker shown in Figs. 1 and 2, the solenoid mechanism may be readily held in place by means of a pair of angle brackets 55 secured to opposite sides of the ring 20 and secured also to the back por tion of the body. 40. Suitable wires for energizing the solenoids, (one for each solenoid and a common return), may pass into the device in the form of a cable 58, as illustrated in Fig. 2, and may be connected to binding posts 57 insulatingly mounted on the ring 20.

In cases where it is desired to use the solenoid mechanism to vibrate the phonograph needle, a suitable supporting base is provided instead of the brackets 55 extending beyond the end of the device. Such base may conveniently be a sheet metal strip 60 fastened to the underside of the ring 20 and extending in each direction and turned downwardly in the form of supporting legs 61 as shown in Figs. 6 and 7. For such an installation as this it is desirable to provide a casing about the solenoid mechanism. Such casing is illustrated at 65. It may be readily made of sheet metal or similar material and house the device and be secured to the down-turned legs 61 thereot'as shown. The casing has a suitable hole 67 at its top through which projects the armature lever 30. The end of the lever in this case is preferably made with a suitable indentation, in which the needle of the phonograph may be placed.

In order that the needle or stylus may be reverse result,

leeches positively given the lateral movementscorresponding to those ordinarily given by the groove of a phonograph disc record, as previously stated herein, advantageously receive the point of the me die to a suitable depth as indicated Fig. 7.' T his indentation is preferably in the nature of a sharp depression or groove, into which the end of the needle projects, being held there, by the weight of the pivoted portion of the usual reproducer mechanism, with the result that thevibrations of varying amplitude are correspondingly transmitted from the armature lever through the needle.

to the phonograph diaphragm. However, if a sharp needle is used it has been found to make its own depression vibrating memher, by the weight of the phonograph sound box such as to make a satisfactory connection. It is also obvious that it may be readily removed and replaced in operating position on the record, by merely lifting the needle from the vibrating lever and placing it upon the record in the usual manner.

As shown in Figs; 6 and 7, indicates a phonograph sound arm, 71 the reproducer box thereof carrying the diaphragm 72, and the reproducer lever 73 pivoted at 7 t. The

screw '7 5 clamps the needle 76 in the usual manner. Our-device may simply rest by gravity on the stationary phonograph table 79. being placed at the side of the rotating table in a convenient position with the axis of the solenoid device extending substantially radially of the rotating table. The device is comparatively small and the movement allowed to the reproducer box and the sound arm enables the reproducer needle to be placed on the end of the armature lever without any change whatsoever in the phonograph arrangements.

We will now describe the means by which the illustrated variable current impulses into solenoid variations of the same frequency to cause impulses may be translated in one direction to strengthen one solenoid and at the same time weaken the other solenoid and those in the other direction to effect the it being understood that such translating means is identical whether the armature lever be directly connected with the diaphragm or operate the phonograph needle or utilize its vibrations in another manner. It will also be understood that in. makin this novel arrangement of'a magnetic eVice with a vibrating member coacting with the usual reproducer mechanism of a phonograph,

in the manner described, is not limited to the precise arrangement shown and described herein for translating d the variable current into mechanical tions.

in the diagram, able vibra- Fig. 8, 80 indicates a suittransformer which as shown, has a pnthis indentation may ductors 83 with the input the grid 87 of the tube 84 mary 81 and a secondary 82, though if de sired an autotrenstormer may be employed havin a winding corresponding to such Seconary, or in fact any suitable device may be used for coupling the output con-' portion of our translating system. 8% and 84 designate a pair oi electronvalves'in the form of vacuum tubes of the usual filament, grid and plate type familiar in radio reproductions. 86 designates a rheostat for controllin the filament of the two tubes. cate suitable batteries.

The circuitsin the diagram may be traced as follows: From the grid 87 of the tube 84 a conductor 90 extends to one end of the secondary 82, while a conductor 91 extends from the other end of the secondary to the grid 87* of the tube 84. A line 93 extends from'the plate 88 of the tube 84 to the solenoids 10 and a line 94 extends from the plate 88" of the tube 84" to the other solenoid 10' 95 indicates a common return from the two solenoids, which is connected to the plus side to the B battery. The'minus side of the B battery is connected by a line- 96 which branches and passes'to the two filaments 89* and 89", respectively. 97 indicates the common return from the two fi1aments which is connected to the filament rheostat 86. From the rheostat a line 98 leads to the plus side of the A battery, which is connected on its other side to the line 96. Another connection from this line 96 leads to the plus side of the C battery, and from the other side of this battery a line 99 leads to the c'enter of the secondary transformer winding 82.

The controlling members of the electron valves are the grids; By causing the Volt ages on the grids to fluctuate in respect to the filament voltage, the plate currents from the 1B battery whichilow in the coils of reproducer will fluctuate correspondingly. If is more positive than the filament (heated by the A battery) then the current in the coil l0 will be stronger than normal. it, however, the grid 87 has a voltage which is negative in respect to the filament, it will cause the plate current in the same coil to diminish below normal value,

According to the diagram of connections shown the input transformer has its winding tapped in a way that it grid 87 becomes more positive than the normal value then grid 87 must necessarily become, negative to the same extent, and vice versa. Thus, if a feeble telephone current be caused to ow in the coupling transformer, the result will be a fluctuation of thevoltages on the two grids in such a manner that for an instant when the voltages on either grid becomes more positive than the normal then A, B and C lndisimultaneously the voltage on the other grid will become correspondingly more negative than normal.

The C battery is used for the purpose of i5 fixing the normal voltage on both grids to a definite value in respect to the filament voltage, in order to allow the valves to operate on the proper part or" thelr characteristic curves.

Since the action of the electron valve is such that when the grid voltage becomes more positive, the plate current increases and When the grid voltage becomes more negative the plate current decreases, the ac tion of the reproduc'er is as follows:

lhe mechanical pull on the armature lever is determined by the strength of the currents in the windings of the solenoid coils. Under normal conditions when no telephone currents enter the device the voltages on the grids of the two electron valves are the same and can be stated to have the normal value. this will result in the two plate currents having practically equal strength. and for this reason the magnetic pulls from the two vex opposing coils which 'are connected into .these plate circuits will be equal and will balance each other, causing no motion of the connecting lever or diaphragm.

With an audio-frequency current entering the system, the grid voltages Will fluctuate in opposite directions from the normal at the same frequency. This will cause a similar unbalance of the plate currents and consequently a similar unbalance of the magnetic pulls from the coils. The result \vidl be a mechanical movement of the connecting lever in the direction of the coil having the current which is greaterthan normal. When the incoming telephonic current iiows for an instant in the oppostie direction the resultant'efiect on the lever will be in the opposite direction. In this in inner it: can he seen that a varying current of udio-i'reouency will cause an. alternating otion oi. the lever.

which will have e frequency and wave form. .liccor'dii A a telephonic current in ti" secondary the coupling transformer cause the lever .rOllOW the produce the emelectron r, esirable,

and stylus, of a pair or" iron clad solenoids positioned in axial alignment and spaced apart, a lever mounted between said solenoids and carrying cores for the respective solenoids and having a depression to receive said stylus, a frame in which said parts are mounted. to maize a unit adapted to stand on a suitable support.

2. In combination with. a phonograph arm, reproducer and needle, of a self-contained unitary electromagnetic vibrator comprising a pair of electromagnetic coils positioned. end to end and spaced apart, and an armature lever mounted between said coils and extending toward the phonograph rcproduccr in a plane parallel with the diaihragm thereol and having means for directly engaging the needle to vibrate it transversely of the plane of the reproducer diaphragm.

3. A sound reproducing device including an electro-magnetic means having a vibrating member, spaced apart magnetic poles adjacent to said vibrating member, an electromagnetic means for causing audio :Er-equency variations in an electric circuit to actuate the vibrating member, a phonograph reproducer including a diaphragm and actuating lever member. means for making an operative connection including a depression on one of said members and a co-acting projection carried by the other of said members.

4. A sound reproducer as claimed in claim 8 characterized in that the vibrating member is a reed secured one end and the magnetic device including a coil adjacent to the reed to cause vibration thereof by variable magnetization.

A. sound reproducing device consisting of a phonograph reproducer having the usual diaphra m and stylus, a vibra ing armature reed having for rec ving and engaging said. styltns {for resiliently mountirg said reed uprightly and magnetic meal "1 for'vihra the reed uhstantially at angles to are plane of the phonograph 6. The com ation rcproducer tone stylus for act ating the k electromagnetic means, in udi read and a mounting the reed projects upwar depressi for race We; eprodur' mounting rests upon a or record depression forming opposed shoulders to reresiliently mountedvibrating member adapt- ,ceive and to operate the lever, said lever ed to have the weight of-said pivoted por- 80 bein readily removable but being engaged tion of the tone arm rest thereon, and means by t e opposed shoulders to cause positive connecting said vibrating member and said vibration of the lever in two directions of lever for positively transmitting said vibra-- movement of the vibrating member wheretion in both directions to the phonograph by thevibratory motion of the vertically diaphragm and transversely thereof, said 85 mounted member may be transmitted connection being readily separable by raisthrough said connection in positive and cering the reproducer box mechanism. tain synchronism in the usual plane of 10. In combination a swingable phonovibration of said actuating lever. graph tone arm, a reproducer mechanism 8. The combination of a phonograph tone mounted on the end of the arm and having 40 arm having a reproducer box, diaphragm, an actuating lever and phonograph stylus, a actuating lever and stylus needle, and a magmagnetic device having a vibrating memnetic device having a resiliently mounted ber provided with a depression for receiving vibrating member projecting upwardly and said stylus and presenting shoulders prehaving an upper surface adapted to receive venting swinging of the tone arm when the 4 the point ofthe stylus and means for causstylus rests therein, means for actuating the ing'the said member to vibrate transversely vibrating member transversely ,of the plane relative to said diaphragm, whereby the of the reproducer mechanism whereby the weight of the reproducer box may cause a inertia of the reproducer causes the vibrapositive actuation of the needle when resting tion to be transmitted through the stylus to 9 upon said member. the diaphragm.

9.'The combination of a phonograph tone In testimony whereof we hereunto afiix arm, mounted to swing horizontally and our signatures having its'reproducer box mechanism, in- K cluding the usual actuating lever pivoted to FRANK J. KAEHNI.

move vertically, a magnetic device having a WILLIAM L. KAEHNI. 

